[sdiy] filters, inductors & Q

[René Schmitz]

Hi Jürgen and all,

> Hi Rene,
> 
> but isn't it a pain to wind torroidals? I mean, even compared to
> winding ordinary inductors ...

Well that depends of course on your personal pain threshold. :-P

Not strictly SDIY or audio related but as an example: Just yesterday I 
wound a tuning coil intended for the low end of the RF spectrum, the 
longwave broadcast band. So I needed about 3mH to resonate with a 350pF 
varicon. I used a core that is about 2.5cm in diameter, and I had 
determined its AL value to about 2300nH/N^2. If you do the math(*), that 
means 36 windings. That didn't take long to wind. Generally it gets more 
painful if the AL is low, and if the cores are small. But you can simply 
buy really large cores, with high AL. The larger ones are pretty 
expensive though, but I'm sure this coil would have fit on a cheaper 
FT50-77 or 82-77 as well.

(*) you don't do it your own of course, theres a nice program that does 
it, its called "Mini Ringkern Rechner". It can tell you what wire gauge 
will fit, and how long the wire has to be (minus the ends required to 
hook it up).

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159